1. Field of the Invention
The subject invention relates to honeycomb panels and tables, honeycomb panel and table manufacture, and optical tables including honeycomb and similar structures.
2. Information Disclosure
This information disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and resonableness, and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention and citations which contrast the subject invention or its merits against the background of developments subsequent in time or priority.
Utility and advantages of honeycomb structures, panels and tables in various fields of technology are well known, as may, for instance, be seen from U.S. Pat. No. 3,784,146 by J. W. Matthews, issued Jan. 8, 1974 for a horizontal vibration isolation system U.S. Pat. No. 4,360,184 by W. J. Reid, III, issued Nov. 23, 1982 for a pneumatic device for attenuation of vertical, horizontal and rotational dynamic forces, U.S. Pat. No. 3,606,460, by M. J. Shannon, issued Sep. 20, 1971 and disclosing furniture and table construction with honeycomb panels, U.S. Pat. No. 3,754,812, by H. Mohn, issued Aug. 28, 1973 and disclosing optical elements with honeycomb support plate, U.S. Pat. No. 3,765,993, by S. L. Raffensparger et al, issued Oct. 16, 1973 and disclosing a layup machine for assembling honeycomb core panels, U.S. Pat. No. 4,035,061, issued Jul. 12, 1977 and U.S. Pat. No. 4,182,553, issued Jan. 8, 1980, by N. K. Sheridon, disclosing honeycomb display devices, and U.S. Pat. No. 4,066,249, by J. G. Huber, issued Jan. 3, 1978 and disclosing a modular vacuum work area with honeycomb core; all being herewith incorporated by reference herein.
Reference may also be had to U.S. Pat. No. 3,070,480, by R. C. Breiner, issued Dec. 25, 1962, and U.S. Pat. No. 3,104,194, by A. T. Zahorski, issued Sep. 17, 1963, both of which show honeycomb panels having corrugated sheets interposed between the honeycomb cores and outer panel sheets, and U.S. Pat. Nos. 3,087,565 and 3,087,571, by E. M. Kerwin, Jr., issued Apr. 30, 1963 for apparatus for damping flexural movements.
Reference may also be had to brochures entitled Mechanical Properties of Hexcel Honeycomb Materials, TSB 120, and The Basics on Bonded Sandwich Construction, TSB 124, by Hexcel Corporation (1982 Revision).
For an extensive tutorial discussion on optical honeycomb tables, reference may be had to the 1983-1984 Catalog by the subject assignee, Newport Corporation, pp. 3 et seq., 2nd Edition, including discussion of the multilevel panel systems on pages 40 and 41 thereof.
In this respect, by way of example and not by way of limitation, among the most sensitive applications to which optical tables are put are those involving interferometry, where tolerable relative displacements of reflective elements are measured in fractions of a micron and allowable table top bending or twisting is typically much less than a second of arc.
Even when requirements are less demanding, it is best to choose a table system that offers that kind of performance, thereby eliminating any likelihood of table related problems.
The rigidity of a panel or table used in optical research is one of the primary performance features and, for a given panel thickness and skin, depends largely on the shear modulus of the core.
For these and related reasons, honeycomb cores are greatly preferred for very stable panel and table systems.
In the past, granite plates and slabs were frequently used in laser holography and interferometry work. However, while granite offers great stability, the lack of a generally acceptable means of securing components to granite surfaces, as well as the great weight of granite slabs, is increasingly displacing them from laboratories and similar environments.
A major advantage of honeycomb panels or tables is that their top skin or table leaf can be provided with a large number of mounting holes which have a very minor effect on panel or table rigidity and strength. Typically, such mounting holes are present in great number and are tapped, thereby permitting the mounting of optical instruments and other components in a wide variety of desired locations.
In some applications, the drilling and tapping of holes in the panel or table top skin leaves residues in the cells of the honeycomb core. Where the honeycomb cores have to be very thick between top and bottom skins for high rigidity and stability, contaminants in the honeycomb cells are sometimes difficult to remove.
Reference may in this respect be had to U.S. Pat. No. 3,137,604, by L. R. Bosch, issued Jun. 16, 1964 for a honeycomb structure and process of manufacture, but failing to suggest any solution to the latter problem.
The same applies to the proposal according to U.S. Pat. No. 4,370,372, by W. E. Higgins et al, issued Jan. 25, 1983 for a method of joining honeycomb panels using a fastener element, and to the proposal according to U.S. Pat. No. 3,249,659, by W. D. Voelker, issued May 3, 1966 for a method of making laminated panel structures in which perforations are provided in reinforcing members between internal cells.
Efforts of providing honeycomb panels in non-analogous areas have worked against, rather than for, a solution, as may be seen from U.S. Pat. No. 2,870,857, by E. E. Goldstein, issued Jan. 27, 1959 for a translucent acoustical correction ceiling construction, U.S. Pat. No. 4,294,329, by P. M. Rose et al, issued Oct. 13, 1981 for a double layer attenuation panel, U.S. Pat. No. 4,300,978, by C. E. Whitemore et al, issued Nov. 17, 1981 for a bonding tool for venting honeycomb noise attenuation structures, and U.S. Pat. No. 4,465,725, by F. J. Riel, issued Aug. 14, 1984 for another noise suppression panel.
These proposals teach preservation of internal flow-through capability between internal honeycomb cells in addition to flow-through to the panel environment, which is just the opposite of what would be needed for clean-room compatibility after contamination of cells during manufacture of the panels.
This, then, can cause problems in clean-room, vacuum and other environments where contaminants are able to leave honeycomb cells through apertures in the top skin to an extent producing a noticeable effect in the particular environment.
In this respect, it has been claimed that the use of threaded inserts in lieu of tapped top skin holes avoids the use of oil that could affect delicate optical opponents. Reference may in this respect be had to the brochure entitled Optical Hardware, by Melles Griot (1983), pp. 2 to 6. Among the problems of that approach is, of course, the fact that even a medium sized table of, say, four feet by six feet size, requires over three thousand threaded inserts which have to be individually positioned and attached to the top skin, if mounting holes one inch apart are to be provided in the table top.
Another approach would be to close each tapped mounting hole with a threaded stud, before the honeycomb panel or table is put into service. This, too, would require the use and insertion of thousands of studs in practical applications and, moreover, would, of course, only seal off, but not remove oil and other drilling and tapping residues from honeycomb cells.
According to advertisements by Technical Manufacturing Corp., of Peabody, MA 01960, which have appeared in Photonics, October 1985 and January 1986, and in Lasers & Applications, September 1985, the tapped holes in the vibration isolation table leaf are individually equipped with metal cups projecting into the honeycomb table cells. In the words of the advertisers, every threaded hole in the top surface is enclosed from below with a welded and epoxy-sealed metal cup, and no inserts are used. Those cups do not appear to impart a beneficial structural or dynamic effect to the vibration isolation performance of the table.
This is confirmed in U.S. Pat. No. 4,645,171, by Ulf B. Heide, issued Feb. 24, 1987 to Technical Manufacturing Corporation, and being expressly limited to non load bearing enclosures. References cited in that patent include U.S. Pat. No. 3,176,662, by R. E. Williams, issued Apr. 6, 1965 for an illustrator's pen holder desk set and components therefor, U.S. Pat. No. 3,456,806, by S. M. Borston, issued Jul. 22, 1969, for a hair curler stand, U.S. Pat. No. 3,601,343, by A. H. Sivaslian, issued Aug. 24, 1971, for a strain-free mount having beamlike support elements, U.S. Pat. No. 3,836,416, by R. L. Ropiequet, issued Sep. 17, 1974, for non-woven thermoplastic fabrics including filaments extruded through orifices in the die of an extrusion chamber, U.S. Pat. No. 4,221,014, by S. L. Davidson, issued Sep. 9, 1980, for a post storage rack having openings in a support plate for drainage and for accommodation of projecting post ends, U.S. Pat. No. 4,241,892, by I. B. Morris, issued Dec. 30, 1980, for an appliance skidboard having top and bottom perforations, and Federal Republic of Germany Patent 836 401, by Wilhelm Dichmann II, issued Apr. 10, 1952, for method and table for retaining papers, cardboard, plywood, metal foil, and the like, having an apertured table top on a vacuum chamber. Another U.S. Pat. No. 4,666,748, by Isaac Rinkewich, issued May 19, 1987, discloses an article of furniture composed of a plurality of curved sections, while U.S. Pat. No. 4,913,953, by K. M. Prewo et al, issued Apr. 3, 1990, discloses integral chopped fiber reinforced glass or glass-ceramic structures, having a grid array of chambers.
None of these references suggest a solution for the problem at hand.
On the other hand, the common assignee hereof, as shown in the above mentioned parent U.S. Pat. No. 4,621,006, has provided clean-room compatible table systems which are relatively easy to manufacture, but are very effective in practice.
Reference may in this respect be had to the above mentioned Second Edition of the Newport Corporation 1983-1984 Catalog, including p. 32, second paragraph, and generally to The Newport Catalog No. 100, published 1987, and particularly to section A thereof, on Vibration-Isolated Table Systems.